Nck is a unique type of oncoprotein which has no enzymatic activity itself, yet consists of several SH2 and SH3 motifs and is involved in signal transduction that is induced by many growth hormones. The aim of the project is to crystallize nck protein and determine its structure. We are using mass spectrometry to check the recombinant nck protein for modifications as well as for the identification of different proteolytic fragments of the protein to help define the tightly folded domains of the protein.